Acute and chronic electrical signal therapy for obesity

ABSTRACT

Apparatus is provided for treating a condition such as obesity. The apparatus includes a set of one or more electrodes, which are adapted to be applied to one or more respective sites in a vicinity of a body of a stomach of a patient. A control unit is adapted to drive the electrode set to apply to the body of the stomach a signal, configured such that application thereof increases a level of contraction of muscle tissue of the body of the stomach, and decreases a cross-sectional area of a portion of the body of the stomach for a substantially continuous period greater than about 3 seconds.

FIELD OF THE INVENTION

[0001] The present invention relates generally to treatment of obesity,and specifically to invasive techniques and apparatus for treatingobesity.

BACKGROUND OF THE INVENTION

[0002] Invasive treatments for obesity are often recommended forpatients with a body mass index (mass/height² [kg/m²]) which is greaterthan 35 or 40. For such patients, their weight is commonly associatedwith increased risk of heart disease, diabetes, and arthritis.Preferably, the invasive treatments are accompanied by changes inlifestyle, such as improved eating habits and an appropriate exerciseregimen.

[0003] U.S. Pat. Nos. 6,067,991 to Forsell, 5,601,604 to Vincent, and5,234,454 to Bangs, and U.S. Pat. Nos. 5,449,368, 5,226,429 and5,074,868 to Kuzmak, which are incorporated herein by reference,describe mechanical instruments for implantation in or around thestomach of an obese patient.

[0004] U.S. Pat. No. 5,690,691 to Chen et al., which is incorporatedherein by reference, describes a gastric pacemaker for treating obesityand other conditions. The pacemaker includes multiple electrodes whichare placed at various positions on the gastrointestinal (GI) tract, andwhich deliver phased electrical stimulation to pace peristaltic movementof material through the GI tract.

[0005] U.S. Pat. No. 5,423,872 to Cigaina, which is incorporated hereinby reference, describes apparatus for applying electrical pulses to thedistal gastric antrum of a patient, so as to reduce the motility of thestomach and to thereby treat obesity or another condition.

[0006] U.S. Pat. Nos. 5,188,104 and 5,263,480 to Wernicke et al., whichare incorporated herein by reference, describe a method for stimulatingthe vagus nerve of a patient so as to alleviate an eating disorder.

[0007] U.S. Pat. Nos. 6,104,955, 6,091,992, and 5,836,994 to Bourgeois,6,026,326 to Bardy, and 3,411,507 to Wingrove, which are incorporatedherein by reference, describe the application of electrical signals tothe GI tract to treat various physiological disorders.

[0008] PCT Patent Publication WO 99/03533 to Ben-Haim et al., entitled,“Smooth muscle controller,” and U.S. patent application Ser. No.09/481,253 in the national phase thereof, both of which are assigned tothe assignee of the present patent application and are incorporatedherein by reference, describe apparatus and methods for applying signalsto smooth muscle so as to modify the behavior thereof. In particular,apparatus for controlling the stomach is described in which a controllerapplies an electrical field to electrodes on the stomach wall so as tomodify the reaction of muscle tissue therein to an activation signal,while not generating a propagating action potential in the tissue. Inthe context of the present patent application and in the claims, the useof such a non-excitatory signal to modify the response of one or morecells to electrical activation thereof, without inducing actionpotentials in the cells, is referred to as Excitable-Tissue Control(ETC). Use of an ETC signal is described with respect to treatingobesity, by applying the ETC signal to the stomach so as to delay orprevent emptying of the stomach. In addition, a method is described forincreasing the motility of the gastrointestinal tract, by applying anETC signal to a portion of the tract in order to increase thecontraction force generated in the portion.

[0009] PCT Patent Publication WO 97/25098, to Ben-Haim et al., entitled“Electrical muscle controller,” and the corresponding U.S. patentapplication Ser. No. 09/101,723, which are assigned to the assignee ofthe present patent application and are incorporated herein by reference,describe methods for modifying the force of contraction of a heartchamber by applying an ETC signal to the heart.

SUMMARY OF THE INVENTION

[0010] It is an object of some aspects of the present invention toprovide improved apparatus and methods for treatment of medicalconditions which relate to the gastrointestinal tract.

[0011] It is a further object of some aspects of the present inventionto provide improved apparatus and methods for treating obesity.

[0012] In preferred embodiments of the present invention, apparatus fortreating a condition such as obesity comprises a set of one or moreelectrodes which are applied to one or more sites of thegastrointestinal (GI) tract of a patient. A control unit preferablydrives the electrode set to apply an Excitable-Tissue Control (ETC)signal to the GI tract, so as to modulate contraction of muscles of thegastrointestinal tract and to thereby treat the condition.

[0013] In a preferred embodiment, the electrodes are applied to thestomach, and the control unit drives the electrodes to apply anenhancement signal which includes, as appropriate, the ETC signal and/oran excitatory signal. Thus, the enhancement signal may inducecontractions and/or increase or otherwise modify the contraction forcesgenerated by muscles of the stomach.

[0014] For some applications, the enhancement signal is applied so as tomodify a contraction pattern of some of the stomach's muscles, in orderto reduce the cross-sectional area of a portion of the stomach. Thenarrow ring thereby generated reduces the volume of a region of thestomach, and increases the sensation of satiety felt by the patientcompared to that which would be felt without the application of thisembodiment of the invention. For example, the enhancement signal maycause an “indenting” of the stomach wall, whereby food is limited in itsability to vacate the esophageal region of the stomach. Consequently,this portion of the stomach is stretched more than usual for the volumeof food ingested, and an earlier sensation of satiety is induced. Thisembodiment thus employs electrical signals to cause a narrowing of thestomach analogous to that produced mechanically by the gastric bandsdescribed in the Background section of the present patent application.Unlike these prior art mechanical bands, however, this application ofthe present invention allows the extent of the narrowing to be moderatedin real time by the control unit without mechanical intermediaries(e.g., modulation of fluid pressure).

[0015] Alternatively or additionally, the enhancement signal is applied,prior to and/or during a meal, so as to reduce the overall size of thestomach, thereby increasing the tension in the wall of the stomach whenfood is in the stomach. This increased tension typically yields acorresponding increase in the patient's sensation of satiety, and thussubstantially reduces the likelihood of the patient overeating.

[0016] Further alternatively or additionally, repeated application ofthe enhancement signal engenders a long-term shortening of muscle fibersof the stomach, and, consequently, a reduction of the size of thestomach, even at times when the signal is not being applied. Thus, forexample, the enhancement signal may be applied, intermittentlythroughout the day, over a period of days, weeks, or months, so as toinduce desired structural changes in the stomach which last, preferably,for at least several days or weeks after removal of the signal.Advantageously, due to the stomach's reduced size, it is typicallystretched during and after a meal to a greater extent than would occurwithout application of the enhancement signal, and thus greatersensations of satiety are felt by the patient. Optionally, the signalmay be applied when the patient's stomach is expected to be relativelyempty (e.g., each morning for one hour prior to the patient waking up),so as to maximize the extent to which the muscle fibers are able toshorten in response to the signal.

[0017] For some patients, it is desirable to apply the enhancementsignal according to a schedule, whereby constriction of the stomachinduces a feeling of satiety at times when the patient might choose toeat but should not be eating. At other times, e.g., when the patient issleeping, the signal is typically not applied. Alternatively oradditionally, the enhancement signal is (a) applied during one or moremeals during the day, so as to reduce the patient's appetite duringthose meals, and (b) removed during meals eaten during the remainder ofthe day, so as to prevent nutritional deficiencies which might occur insome patients from any inappropriate, excessive use of the signalsdescribed herein.

[0018] In a preferred embodiment, the enhancement signal is applied tomuscle in one portion of the stomach, so as to induce and/or modify acontraction of the stimulated muscle which, in turn, causes stretchingof stretch-receptors in an adjacent portion of the stomach. This form ofcontraction-mediated stretching simulates the normal satiety signalingof the stomach's stretch-receptors, without the patient having eaten thequantities of food which would normally be required to trigger thissatiety response.

[0019] Alternatively or additionally, some or all of the electrodes areplaced in a vicinity of the pyloric sphincter, and the control unitdrives the electrode set to apply the enhancement signal so as toincrease a contraction force of the sphincter. The increased forcetypically reduces the sphincter's cross-section, and thereby generallyextends a period of time in which partially-digested food remains in thestomach.

[0020] In a preferred embodiment, one or more electrodes are applied toor in a vicinity of respective sites of the arterial supply of thepatient's small intestine. Typically, the control unit drives some orall of the electrodes to apply signals which cause a controllable levelof constriction of the arteries to which these electrodes are coupled.The constriction produced thereby preferably transiently andcontrollably reduces the blood flow to the small intestine, and, it isbelieved, thereby reduces the total number of calories which areultimately absorbed into the patient's bloodstream during and aftereating a meal.

[0021] There is therefore provided, in accordance with a preferredembodiment of the present invention, apparatus for treating a condition,including:

[0022] a set of one or more electrodes, adapted to be applied to one ormore respective sites in a vicinity of a stomach of a patient; and

[0023] a control unit, adapted to drive the electrode set to apply anExcitable-Tissue Control (ETC) signal to the sites, configured such thatapplication thereof decreases a cross-sectional area of at least aportion of the stomach.

[0024] Preferably, the set of one or more electrodes includes a firstset of one or more electrodes, and the apparatus includes a second setof one or more electrodes, adapted to be applied to one or morerespective sites in a vicinity of a pyloric sphincter of the stomach.The control unit is preferably adapted to drive the second electrode setto apply an ETC signal configured such that application thereofincreases a contraction force of the sphincter and extends a period oftime in which partially-digested food remains in the stomach.

[0025] Further preferably, the control unit is adapted to configure theETC signal such that application thereof decreases the cross-sectionalarea of the portion of the stomach by at least 20%, for a substantiallycontinuous period greater than about one minute.

[0026] Still further preferably, the portion of the stomach includes afirst portion of the stomach, and the control unit is adapted toconfigure the ETC signal such that ingestion of food by the patient inconjunction with application of the ETC signal to the first portioninduces stretching of a stretch-receptor in a second portion of thestomach that induces a sensation of satiety.

[0027] In a preferred embodiment, the control unit is adapted to drivethe electrode set to apply the signal over a sufficient time period soas to engender a long-term structural change of the stomach.

[0028] Typically, the electrode set is adapted to be applied in contactwith muscle tissue of the stomach.

[0029] The control unit is preferably adapted to configure the ETCsignal such that the decreased cross-sectional area impedes passage ofingesta through the stomach.

[0030] Alternatively or additionally, the control unit is adapted toconfigure the ETC signal such that application thereof decreases avolume of the stomach.

[0031] In some preferred embodiments of the present invention, thecontrol unit is adapted to configure a timing parameter of the ETCsignal responsive to timing of natural gastric electrical activity. TheETC signal is typically applied as a series of biphasic pulses.Preferably, the control unit is adapted to configure the ETC signal tohave a duration of at least about 1 second. Further preferably, theduration is at least about 3 seconds.

[0032] For some applications, the apparatus includes at least onestimulating electrode, and the control unit is adapted to drive thestimulating electrode to apply an excitatory signal to muscle tissue ofthe stomach in conjunction with driving the electrode set to apply theETC signal. In these cases, the control unit is typically adapted todrive the stimulating electrode to apply gastric pacing pulses to thestomach.

[0033] Preferably, the control unit is adapted to receive a patientsignal, input by the patient, and to drive and withhold driving theelectrode set responsive to the patient signal.

[0034] The control unit is typically adapted to drive the electrode setin accordance with a schedule programmed into the control unit. Forexample, the control unit may be adapted to drive the electrode setduring at least one meal eaten by the patient during a 24 hour period,and to withhold driving the electrode set during another meal eaten bythe patient during the 24 hour period. Alternatively or additionally,the control unit is adapted to withhold driving the electrode set duringtime periods designated as times when the patient generally does noteat.

[0035] For some applications, the control unit is adapted to drive atleast one of the electrodes to apply an excitatory pulse in conjunctionwith the ETC signal. Preferably, the control unit is adapted to drivethe at least one electrode to apply the excitatory pulse as a biphasicpulse. Alternatively or additionally, the control unit is adapted todrive the at least one electrode to initiate applying the ETC signal atleast about 100 ms following a termination of the excitatory pulse.Preferably, the control unit is adapted to drive the at least oneelectrode to initiate applying the ETC signal less than about 1000 msfollowing a termination of the excitatory pulse.

[0036] Preferably, the control unit is adapted to drive the electrodeset while the patient is eating. The control unit may, for example, beadapted to receive a patient signal, input by the patient, indicative ofthe patient eating. In this case, the control unit is preferably adaptedto receive by way of the patient signal an indication of a nutritionalquality of food being eaten by the patient and to configure a parameterof the ETC signal responsive to the patient signal.

[0037] Alternatively or additionally, the apparatus includes a sensorwhich is adapted to convey to the control unit a signal responsive tothe patient eating. As appropriate, the sensor may include a blood sugarsensor or a mechanical sensor. Alternatively or additionally, the sensorincludes a sensing electrode, adapted to be coupled in a vicinity of agastrointestinal tract of the patient. For some applications, thesensing electrode includes one of the one or more electrodes.

[0038] Preferably, the sensor is adapted to convey the signal responsiveto a quantity of food ingested by the patient, and the control unit isadapted to withhold driving the electrode set, as appropriate,responsive to the quantity (e.g., if the quantity is less than athreshold quantity).

[0039] In a preferred embodiment, the control unit is adapted toconfigure the ETC signal such that application thereof decreases thecross-sectional area of a region of the stomach, and maintains thedecreased cross-sectional area in the region for a duration greater thanabout 10 seconds.

[0040] In a preferred embodiment, the control unit is adapted toconfigure the ETC signal such that application thereof increasesintra-gastric pressure, thereby inducing a sensation of satiety.

[0041] For some applications, the apparatus includes a second set of oneor more electrodes, adapted to be applied to one or more respectivesites in a vicinity of the lower-esophageal sphincter. The control unitis preferably adapted to drive the second electrode set to apply asignal to the sphincter, configured such that application thereofincreases a contraction force generated by the sphincter.

[0042] There is further provided, in accordance with a preferredembodiment of the present invention, apparatus for treating a condition,including:

[0043] a set of one or more electrodes, adapted to be applied to one ormore respective sites in a vicinity of a pyloric sphincter of a stomachof a patient; and

[0044] a control unit, adapted to drive the electrode set to apply anExcitable-Tissue Control (ETC) signal to the sites, configured such thatapplication thereof increases a contraction force of the sphincter andextends a period of time, in which partially-digested food remains inthe stomach.

[0045] Preferably, the control unit is adapted to configure the ETCsignal such that driving the electrode set to apply the ETC signalincreases the contraction force for a substantially continuous periodgreater than about 1 minute.

[0046] As appropriate, the electrode set may be adapted to be applied incontact with muscle tissue of an antral portion of the stomach and/or incontact with muscle tissue of the sphincter.

[0047] There is still further provided, in accordance with a preferredembodiment of the present invention, apparatus for treating a condition,including:

[0048] a set of one or more electrodes, adapted to be applied to one ormore respective sites in a vicinity of a body of a stomach of a patient;and

[0049] a control unit, adapted to drive the electrode set to apply tothe body of the stomach a signal configured such that applicationthereof increases a level of contraction of muscle tissue of the body ofthe stomach, and decreases a cross-sectional area of a portion of thebody of the stomach for a substantially continuous period greater thanabout 3 seconds.

[0050] Preferably, the control unit is adapted to configure the signalsuch that application thereof decreases the cross-sectional area of theportion for a substantially continuous period greater than about 10seconds.

[0051] There is yet further provided, in accordance with a preferredembodiment of the present invention, apparatus for treating a condition,including:

[0052] a set of one or more electrodes, adapted to be applied to one ormore respective sites in a vicinity of a first portion of a stomach of apatient; and

[0053] a control unit, adapted to drive the electrode set to apply tothe portion of the stomach a signal configured such that applicationthereof increases a level of contraction of muscle tissue of theportion, and configured such that ingestion of food by the patient inconjunction with application of the signal induces stretching of astretch-receptor in a second portion of the stomach.

[0054] Preferably, the control unit is adapted to drive the electrodeset to apply the signal to a body of the stomach, and to configure aparameter of the signal such that the increased level of contraction ofthe muscle tissue impedes passage of ingesta through the stomach andincreases a level of tension in a fundic wall of the stomach.

[0055] There is also provided, in accordance with a preferred embodimentof the present invention, apparatus for treating a condition, including:

[0056] a set of one or more electrodes, adapted to be applied to one ormore respective sites on an arterial supply of small intestine of apatient; and

[0057] a control unit, adapted to drive the electrode set to apply asignal to the sites, configured such that application thereof inducesconstriction of one or more arteries in the arterial supply anddecreases a quantity of digestion products which are absorbed into bloodof the patient from the small intestine.

[0058] Preferably, the control unit is adapted to determine anapproximate time of initiation of eating, and to initiate driving theelectrode set to apply the signal at least ten minutes subsequentthereto. Typically, the control unit is adapted to determine theapproximate time of initiation of eating responsive to receiving apatient signal, input by the patient.

[0059] In a preferred embodiment, the apparatus includes a sensor whichis adapted to convey to the control unit a signal indicative of foodbeing in a gastrointestinal tract of the patient.

[0060] There is additionally provided, in accordance with a preferredembodiment of the present invention, apparatus for treating a condition,including:

[0061] a set of one or more electrodes, adapted to be applied to one ormore respective sites of a stomach of a patient; and

[0062] a control unit, adapted to drive the electrode set to apply tothe stomach, over a sufficient time period, a sequence of pulsesconfigured so as to engender a long-term structural change of thestomach.

[0063] Preferably, the control unit is adapted to configure the sequenceof pulses as an Excitatory-Tissue Control (ETC) signal. Alternatively oradditionally, the control unit is adapted to configure a parameter ofthe sequence of pulses such that the application of the pulses over thetime period is such as to engender a continuation of the structuralchange for at least two days following a termination of the applicationof the pulses.

[0064] Preferably, the control unit is adapted to configure a parameterof the sequence of pulses such that the application of the pulses overthe time period is such as to reduce a characteristic length of musclefibers of the stomach. Alternatively or additionally, the control unitis adapted to configure a parameter of the sequence of pulses such thatthe application of the pulses over the time period is such as to reducea characteristic size of the stomach.

[0065] For some applications, the control unit is adapted to drive theelectrode set to apply the pulses for at least two days. Preferably, thecontrol unit is adapted to drive the electrode set to apply the pulsesfor at least two weeks.

[0066] In a preferred embodiment, the control unit is adapted to drivethe electrode set in accordance with a schedule programmed into thecontrol unit. For example, the control unit may be adapted to drive theelectrode set at times when the patient's stomach is generally empty, orduring a meal eaten by the patient.

[0067] There is yet additionally provided, in accordance with apreferred embodiment of the present invention, a method for treating acondition, including:

[0068] applying an Excitable-Tissue Control (ETC) signal to one or moresites in a vicinity of a stomach of a patient; and

[0069] configuring the ETC signal such that application thereof to theone or more sites decreases a cross-sectional area of at least a portionof the stomach.

[0070] There is still additionally provided, in accordance with apreferred embodiment of the present invention, a method for treating acondition, including:

[0071] applying an Excitable-Tissue Control (ETC) signal to one or moresites in a vicinity of a pyloric sphincter of a stomach of a patient;and

[0072] configuring the ETC signal such that application thereof to theone or more sites increases a contraction force of the sphincter andextends a period of time in which partially-digested food remains in thestomach.

[0073] There is also provided, in accordance with a preferred embodimentof the present invention, a method for treating a condition, including:

[0074] applying a signal to one or more sites in a vicinity of a body ofa stomach of a patient; and

[0075] configuring the signal such that application thereof to the oneor more sites increases a level of contraction of muscle tissue of aportion of the body of the stomach, and decreases a cross-sectional areaof the portion for a substantially continuous period greater than about3 seconds.

[0076] There is further provided, in accordance with a preferredembodiment of the present invention, a method for treating a condition,including:

[0077] applying a signal to one or more sites in a vicinity of a firstportion of a stomach of a patient; and

[0078] configuring the signal such that the application thereofincreases a level of contraction of muscle tissue of the portion andstretches a stretch-receptor in a second portion of the stomach.

[0079] There is still further provided, in accordance with a preferredembodiment of the present invention, a method for treating a condition,including:

[0080] applying a signal to one or more sites on an arterial supply ofsmall intestine of a patient; and

[0081] configuring the signal such that application thereof to the sitesinduces constriction of one or more arteries in the arterial supply anddecreases a quantity of digestion products which are absorbed into bloodof the patient from the small intestine.

[0082] There is yet further provided, in accordance with a preferredembodiment of the present invention, a method for treating a condition,including:

[0083] applying a sequence of pulses over a time period to one or moresites of a stomach of a patient; and

[0084] configuring the sequence of pulses such that application thereofto the one or more sites engenders a long-term structural change of thestomach.

[0085] The present invention will be more fully understood from thefollowing detailed description of the preferred embodiments thereof,taken together with the drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

[0086]FIG. 1A is a schematic illustration of a stomach, showing theplacement of electrodes and sensors thereon, in accordance with apreferred embodiment of the present invention;

[0087]FIG. 1B is a schematic illustration of the stomach of FIG. 1A, ina contracted state thereof responsive to the application of anelectrical signal thereto, in accordance with a preferred embodiment ofthe present invention;

[0088]FIG. 2 is a schematic block diagram of a control unit, whichgenerates signals to be applied to the electrodes shown in FIG. 1A, inaccordance with a preferred embodiment of the present invention;

[0089]FIG. 3A is a graph showing an electrical signal applied to thestomach of a dog, in accordance with a preferred embodiment of thepresent invention, and deformations of the stomach produced in responseto the applied signal;

[0090]FIGS. 3B and 3C are graphs illustrating details of the electricalsignal shown in FIG. 3A, in accordance with respective preferredembodiments of the present invention; and

[0091]FIG. 4 is a schematic illustration of the vasculature supplying asection of small intestine, showing the placement of electrodes andsensors thereon, in accordance with a preferred embodiment of thepresent invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0092] Reference is now made to FIGS. 1A and 1B. FIG. 1A is a schematicillustration of gastric control apparatus 18, which applies electricalenergy to modify the activity of a portion of the gastrointestinal tractof a patient, in accordance with a preferred embodiment of the presentinvention. Apparatus 18 typically comprises an implantable or externalcontrol unit 90, which drives one or more electrodes 100 to apply anenhancement signal to respective sites on or in a vicinity of thepatient's stomach 20 and/or elsewhere on or in a vicinity of sites onthe gastrointestinal tract. At least some of the sites are preferablylocated on the body of the stomach, i.e., that portion of the stomachlocated between the lower-esophageal sphincter and the pyloricsphincter. The enhancement signal is preferably configured so as tomodulate contraction of muscles of the stomach and to thereby treat acondition such as obesity. FIG. 1B is a schematic illustration ofstomach 20 in a contracted state thereof, responsive to the applicationof the enhancement signal thereto in accordance with a preferredembodiment of the present invention.

[0093] Preferably, the enhancement signal includes, as appropriate, anExcitable-Tissue Control (ETC) signal and/or an excitatory signal whichinduces contraction of muscles of the stomach. Aspects of ETC signalapplication are typically performed in accordance with techniquesdescribed in the above-referenced PCT Publications WO 99/03533 and WO97/25098 and their corresponding U.S. national phase application Ser.Nos. 09/481,253 and 09/101,723, mutatis mutandis. For some applications,the ETC signal is applied responsive to natural electrical activity ofstomach 20, for example, after a designated delay following a detectedactivation of a portion of the stomach. For these applications, it ispreferable to use apparatus and methods described in Israel PatentApplication 129,257, entitled “Trigger-based regulation of excitabletissue control in the heart,” mutatis mutandis. This application isassigned to the assignee of the present invention and is incorporatedherein by reference. Alternatively, the ETC signal is applied subsequentto an artificial gastric pacing pulse, as described hereinbelow.

[0094] Typically, control unit 90 drives electrodes 100 to apply theenhancement signal so as to create a contraction pattern of some of themuscles of stomach 20, such as the contraction shown in FIG. 1B, inorder to reduce the cross-sectional area of a portion 22 of the stomach.This reduction is believed to increase the sensation of satiety felt bythe patient compared to that which was felt prior to application of theenhancement signal. Typically, the enhancement signal is configured suchthat the cross-sectional area of the stomach is reduced by at least 20%,and this reduction is maintained in one region of the stomach for aperiod of at least 1 minute. It is to be understood that for someapplications, greater or lesser reductions in cross-sectional area maybe desirable, and these may be maintained for periods greater or lessthan 1 minute.

[0095] Electrodes 100 preferably comprise one or more signal applicationelectrodes 30, which may also operate in a sensing mode. In addition,one or more dedicated local sense electrodes 74 are preferably placed onor in stomach 20, and convey electrical signals to control unit 90responsive to natural gastric electric activity. Further preferably, oneor more mechanical sensors 70 (e.g., accelerometers, force transducers,strain gauges, or pressure gauges) are coupled to the control unit andare placed on or in the stomach. Alternatively or additionally, one ormore supplemental sensors 72 (e.g., pH sensors, blood sugar sensors,intragastric pressure sensors and/or sonometric sensors) are coupled tothe control unit and are placed on or in the gastrointestinal tract orelsewhere on or in the patient's body. The control unit preferablymodifies the waveform applied through electrodes 100 responsive tosignals from sensors 70 and 72 and local sense electrodes 74, asdescribed hereinbelow with reference to FIG. 2. Typically, control unit90 and the above-mentioned electrodes and sensors are permanently orsemi-permanently implanted in or coupled to the patient's body. (Forclarity, connections between control unit 90 and only some of theelectrodes and sensors are shown in FIG. 1A.)

[0096] Electrodes 100 are typically coupled to the serosal layer of thestomach and/or inserted into the muscular layer of the stomach.Alternatively or additionally, the electrodes are coupled elsewhere onthe stomach, gastrointestinal tract, or to other suitable locations inor on the patient's body. The number of electrodes and sensors, as wellas the positions thereof, are shown in FIG. 1A by way of example, andother sites on stomach 20 or in a vicinity thereof are appropriate forelectrode and sensor placement in other applications of the presentinvention. Different types of electrodes known in the art are typicallyselected based Son the specific manifestation of the patient'scondition, and may comprise stitch, coil, screw, patch, basket, needleand/or wire electrodes, or substantially any other electrode known inthe art of electrical stimulation or sensing in tissue.

[0097] Preferably, control unit 90, electrodes 100, and the varioussensors described herein are implanted in the patient in a mannergenerally similar to that used to implant gastric pacemakers or otherapparatus for stimulating the gastrointestinal tract which are known inthe art. As appropriate, techniques described in one or more of thepatents cited in the Background section of the present patentapplication may be adapted for use with these embodiments of the presentinvention.

[0098]FIG. 2 is a schematic block diagram of control unit 90, inaccordance with a preferred embodiment of the present invention.Mechanical sensors 70, supplemental sensors 72, local sense electrodes74, and electrodes 100 are preferably coupled to provide feedbacksignals to a digestive activity analysis block 80 of control unit 90.The feedback signals generally provide block 80 with information aboutvarious aspects of the stomach's present state (e.g., empty or full) andthe stomach's level of activity, so as to enable block 80 to analyze thesignals and actuate control unit 90 to modify the electrical energyapplied to electrodes 100 responsive to the analysis. Preferably, theenhancement signal is adjusted by the control unit responsive to thefeedback signals in order to yield a desired response, e.g., anindication by mechanical sensors 70 of a desired level of musclecontraction within portion 22, or an indication by supplemental sensors72 of maintenance of the patient's blood sugar level within a desiredrange. Advantageously, the ability to turn the enhancement signal on oroff at any time, in order to modulate the stomach's shape, provides agenerally safer and more effective alternative to prior art,purely-mechanical techniques for remodeling the stomach.

[0099] For some applications, control unit 90 drives electrodes 100 toapply the enhancement signal according to a schedule, so as to induceconstriction of stomach 20 at times when the patient should not beeating, or when the patient's eating should be minimized. Alternativelyor additionally, the enhancement signal is (a) applied during one ormore meals during the day, so as to reduce the patient's appetite duringthose meals, and (b) removed during the remainder of the day, so as toprevent counterproductive remodeling of the stomach.

[0100] Alternatively or additionally, the patient activates,deactivates, and modulates the level of signal application in accordancewith physician's instructions, aspects of the patient's diet, or otherfactors. For example, the patient may eat soup and salad at dinner, andthen activate the control unit using operator controls 71, so as toincrease the sense of satiety prior to being presented with a largeselection-of high-calorie options for an entree. The patient maysubsequently input a command for a higher level of signal-applicationduring dessert, such that the patient will feel very full, and, in fact,not have space for the dessert. It is seen through this example thatthis embodiment of the present invention can be used to encourage thepatient to fully satisfy all nutritional needs, while simultaneouslyreducing or eliminating the hunger sensation which the patient wouldotherwise feel if stomach 20 were not in the contracted state induced bythe enhancement signal.

[0101] For some applications, control unit 90 drives electrodes 100 toapply the enhancement signal to muscle in one area of stomach 20, so asto induce a contraction of the stimulated muscle which, in turn, causesstretching of stretch-receptors in an adjacent portion of the stomach.This form of contraction-mediated stretching simulates the normalappetite-reduction action of the stomach's stretch-receptors, withoutthe patient having eaten the quantities of food which would normally berequired to trigger this appetite-reduction response. For example, thecontrol unit may generate an enhancement signal which causes contractionof the corpus of the stomach at the beginning of a meal, whereby asubstantial amount of food will accumulate in the fundus. Thisaccumulation, in turn, increases intra-gastric pressure and stretchesthe fundic walls to a greater extent than would be caused without theapplied enhancement signal. If it is determined that a patient hasintermittent gastro-esophageal reflux episodes in response to theincreased intra-gastric pressure, then it is preferable to additionallyapply the enhancement signal to the lower-esophageal sphincter, so as toincrease the contraction force thereof and reduce or eliminate thereflux.

[0102] Alternatively or additionally, some or all of electrodes 100 areplaced in a vicinity of the pyloric sphincter 24 of stomach 20, andcontrol unit 90 drives these electrodes to apply the ETC signal so as toincrease a contraction force of the sphincter. Although it is known inthe art to apply pacing or other excitatory signals to the sphincterwith the intention of contracting the sphincter and increasing the timein which food remains in the stomach, the inventors believe that theseprior art methods do not effectively achieve a sufficient level ofconstriction of the sphincter, and therefore do not engender the optimumweight loss of the patient. By contrast, application of the ETC signalto muscle in the gastrointestinal tract has been shown (see FIG. 3) tosubstantially increase contraction force above that obtained by pacingalone.

[0103] As shown in FIG. 2, digestive activity analysis block 80typically conveys results of its analysis of the inputs from mechanicalsensors 70, supplemental sensors 72, and electrodes 100 to a “parametersearch and tuning” block 84 of control unit 90, which iterativelymodifies characteristics of the electrical energy applied to stomach 20in order to attain a desired response. Preferably, operating parametersof block 84 are entered, using operator controls 71, by a physician orother human operator of the control unit. Block 84 typically utilizesmultivariate optimization and control methods known in the art in orderto cause one or more of the aforementioned mechanical, electrical,chemical and/or other measured parameters to converge to desired values.

[0104] In general, each one of electrodes 100 may convey a particularwaveform to stomach 20, differing in certain aspects from the waveformsapplied by the other electrodes. The particular waveform to be appliedby each electrode is determined by control unit 90, preferably under theinitial control of the operator. Aspects of the waveforms which are setby the control unit, and may differ from electrode to electrode,typically include parameters such as time shifts between application ofwaveforms at different electrodes, waveform shapes, amplitudes, DCoffsets, durations, and duty cycles. For example, although the waveformsapplied to some or all of electrodes 100 usually comprise a train ofbiphasic square waves following a natural or applied pacing pulse, otherwaveforms, such as a sinusoid, one or more monophasic square waves, or awaveform including an exponentially-varying characteristic, could beapplied to other electrodes. Generally, the shape, magnitude, and timingof the waveforms are optimized for each patient, using suitableoptimization algorithms as are known in the art.

[0105] Preferably, desired signal parameters are conveyed by block 84 toa signal generation block 86 of control unit 90, which generates,responsive to the parameters, electrical signals that are applied byelectrodes 100 to the stomach. Block 86 preferably comprises amplifiers,isolation units, and other standard circuitry known in the art ofelectrical signal generation.

[0106] In an initial calibration procedure, parameter search and tuningblock 84 preferably modifies a characteristic (e.g., timing, magnitude,or shape) of the enhancement signal applied through one of electrodes100, and then determines whether a predetermined response generallyimproves following the modification. For example, one or more ofmechanical sensors 70 may be used to determine the extent to which theshape of stomach 20 changes responsive to corresponding changes in theapplied enhancement signal. In a series of similar calibration steps,block 84 repeatedly modifies characteristics of the energy appliedthrough each of the electrodes, such that those modifications thatimprove the response are generally maintained, and modifications thatcause it to worsen are typically eliminated or avoided. Preferably, thecalibration procedure is subsequently performed by the physician atintermittent follow-up visits, and/or by unit 90 automatically duringregular use of apparatus 18 (e.g., daily).

[0107] In a preferred embodiment, the calibration procedure additionallycomprises determining a schedule for the application of the enhancementsignal at various sites on the stomach. For example, it may bedetermined for some patients that it is advantageous to: (a) apply theenhancement signal to the sites in a wave, which simulates the naturalflow of electrical activity in the stomach, (b) maintain the shapemodification for a specified period (e.g., 5-15 minutes), (c) remove thesignal for a relaxation period (e.g., 1-5 minutes), and (d) return tostep (a).

[0108] Preferably, during the initial calibration procedure, thelocations of one or more of electrodes 100 are varied while theenhancement signal is applied therethrough, so as to determine optimumplacement of the electrodes. In a series of calibration steps, eachelectrode is moved over an area of stomach 20, and an appropriateresponse of the stomach is measured. After the physician considers thata sufficient number of sites have been investigated to characterize thearea, the electrode is returned to the site yielding the best response.Subsequently, other electrodes, placed on, in, or near the stomach aremoved according to the same protocol, so as to achieve substantiallyoptimum placement of some or all of the electrodes.

[0109] Based on results of the calibration procedure and/or an analysisof other factors pertaining to the patient's condition, the physiciantypically determines whether the ETC signal should be applied subsequentto an artificial pacing pulse or in response to natural electricalactivity of the stomach. In the former case, the ETC signal ispreferably applied in a vicinity of a site where standard gastric pacingpulses are applied. Further preferably, the ETC signal is appliedthrough the same electrode as that through which a gastric pacing pulseis applied.

[0110] Alternatively, stomach 20 generates the gastric rhythm,substantially without artificial pacing. In such modes, local senseelectrodes 74 and, optionally, some or all of electrodes 100, conveyelectrical signals to control unit 90, so as to enable parameter searchand tuning block 84 to synchronize the electrical signals applied byelectrodes 100 with the natural electrical activity of the stomach. Itwill be understood that although electrodes 74 and 100 are shown forclarity of explanation as separate entities, a single set of electrodesmay be used to perform both functions.

[0111]FIG. 3A is a graph showing an electrical signal applied to thestomach of a dog, in accordance with a preferred embodiment of thepresent invention, and deformations of the stomach produced in responseto the applied signal. In this experiment, two stitch electrodes wereinserted approximately 3 centimeters apart through the serosa of theantral area of the stomach, into the muscularis. Throughout theexperiment, the electrodes applied 20 mA peak-to-peak biphasic pacingpulses, each phase lasting for 300 milliseconds. Successive pacingpulses were separated by 20 seconds. In addition, during two periods,ETC signals having characteristics described hereinbelow with referenceto FIGS. 3B and 3C were applied following the pacing pulses. Thedeformation of the outer wall of the stomach responsive to the appliedsignals was measured continuously by a strain gauge placed on thestomach between the electrodes.

[0112]FIGS. 3B and 3C are graphs showing details of the applied pacingpulses and ETC signals shown in FIG. 3A, in accordance with respectivepreferred embodiments of the present invention. During the periodlabeled in FIG. 3A, “Pacing & ETC I,” an ETC signal lasting 1000milliseconds was applied starting 500 milliseconds after each pacingpulse. The ETC signal itself comprised a series of biphasic squarecurrent pulses (+10 mA, −10 mA), each phase having a 50 millisecondduration. During the period labeled in FIG. 3A, “Pacing & ETC II,” anETC signal having the same parameters was applied to the stomach, exceptthat the duration of the “ETC II” signal application was 4000milliseconds.

[0113] With reference to FIG. 3A, during an approximately two minutewarm-up period, small deformations are seen to be produced by each ofthe pacing pulses. These deformations are believed to generallycorrespond to the levels of deformation produced due to natural gastricelectrical activity. Following this pacing-only warm-up period, the“Pacing & ETC I” signal described hereinabove was applied for about twominutes, during which increased contraction strength by the dog'sstomach produced increased deformations, which are clearly visible inFIG. 3A. Subsequently, the “ETC I” signal was removed, and a pacing-onlyperiod was recommenced, resulting in a complete return to baseline(pre-ETC) contraction levels. Lastly, during the “Pacing & ETC II”period described hereinabove, deformation of the stomach increasedsignificantly above baseline, and remained significantly above baselinevalues for the approximately two-minute duration of the signalapplication. For clinical applications, similar signals are preferablyapplied through a larger number of electrodes in order to attain andmaintain the constriction of the stomach depicted in FIG. 1B.

[0114]FIG. 4 is a schematic illustration depicting apparatus 118 fortreating obesity or another condition of a patient, in accordance with apreferred embodiment of the present invention. Apparatus 118 preferablycomprises a control unit 190, and one or more electrodes 200 applied toor in a vicinity of respective sites of the arterial supply 130 of thepatient's small intestine 120. If appropriate, some or all of electrodes200 may be placed on the superior mesenteric artery 110, or in avicinity thereof. Typically, control unit 190 drives electrodes 200 toapply signals which cause a controllable level of constriction of thearteries to which these electrodes are coupled. Alternatively oradditionally, other transducers (not shown) are implanted in the patientin a vicinity of arterial supply 130, and are driven by control unit 190to induce some or all of the arteries in supply 130 to contract. Asappropriate, these transducers may induce this contraction usingmechanical or chemical means. The constriction produced by apparatus 118preferably transiently and controllably reduces the blood flow to smallintestine 120, and thereby reduces the total number of calories whichare ultimately absorbed into the patient's bloodstream during and aftereating a meal.

[0115] For some applications, it is advantageous to utilize apparatus118 in conjunction with apparatus 18, in order to reduce the patient'sweight in a quicker manner than would likely be realized when usingeither apparatus alone. Alternatively, apparatus 118 may be used withoutsimultaneous use of apparatus 18, for example, if it is determined thatthe patient is likely to try and “cheat” apparatus 18 by drinkinghigh-calorie liquid foods, whose digestion might not be affected byapparatus 18 to the same extent as that of solid foods. For instance, itis known that many patients who have mechanical gastric-restrictionbands drink high-calorie milk-shakes in order to evade the therapeuticeffects of the mechanical bands.

[0116] Preferably, apparatus and methods described hereinabove withrespect to apparatus 18 are utilized, mutatis mutandis, in the operationof apparatus 118. Thus, for example, control unit 190 may driveelectrodes 200 to apply an ETC signal and/or pulses and/or other signalforms to modulate arterial supply 130. Additionally, control unit 190preferably varies parameters of the applied electrical energy responsiveto feedback from mechanical sensors 70 and/or supplemental sensors 172,which are typically applied to small intestine 120, in a vicinitythereof, or elsewhere on or in the patient's body.

[0117] Preferably, but not necessarily, the electrical energy is appliedat times which are likely to produce maximum weight loss, withoutadversely affecting the patient's nutritional intake, and withoutsignificantly reducing the patient's comfort. Thus, for example, one ofsupplemental sensors 172 may comprise a blood-sugar monitor, whichinhibits control unit 190 from applying the electrical energy when thepatient's blood sugar is below a determined threshold. Alternatively oradditionally, operation of apparatus 118 is initiated or supplementedresponsive to a parameter of the contents of small intestine 120, suchas an indication by sensors 172 of the lipid concentration thereof.Further alternatively or additionally, the patient is enabled toactivate apparatus 118 (e.g., during and after eating dessert, or for adetermined time period when the patient is going to sleep) and todeactivate the apparatus (e.g., when the patient has a headache, or hasorally taken a medication). Still further alternatively or additionally,apparatus 118 is activated a fixed or variable time (e.g., 10-30minutes) following initiation of a meal, when it is expected that somedigestive products will have reached the small intestine.

[0118] Preferably, a calibration period is provided for apparatus 118,which provides some or all of the calibration options describedhereinabove with respect to apparatus 18. In addition, safe signalapplication durations and activation sequences of electrodes 200 arepreferably determined during the calibration period, such that smallintestine 120 continually has a sufficient level of blood flowingtherethrough to support normal activity of the tissue of the smallintestine.

[0119] For some applications, an intestinal enhancement signal isapplied to electrodes 174 coupled to respective sites on small intestine120. Preferably, control unit 190 drives electrodes 174 to apply theintestinal enhancement signal so as to increase the contraction forcegenerated by muscle of small intestine 120. This increased contractionforce, in turn, decreases the period of time in which digestion productsremain in the intestine, and, therefore, decreases the quantity of thesedigestion products which are ultimately absorbed into the patient'sbloodstream. As appropriate, the intestinal enhancement signal maycomprise an ETC component and/or other signals known in the art forstimulating tissue. Moreover, the intestinal enhancement signal may beapplied in combination with, or separately from, the signals applied toelectrodes 100 and/or 200, described hereinabove.

[0120] It will be appreciated by persons skilled in the art that thepresent invention is not limited to what has been particularly shown anddescribed hereinabove. Rather, the scope of the present inventionincludes both combinations and subcombinations of the various featuresdescribed hereinabove, as well as variations and modifications thereofthat are not in the prior art, which would occur to persons skilled inthe art upon reading the foregoing description.

1. Apparatus for treating a condition, comprising: a set of one or moreelectrodes, adapted to be applied to one or more respective sites in avicinity of a stomach of a patient; and a control unit, adapted to drivethe electrode set to apply an Excitable-Tissue Control (ETC) signal tothe sites, configured such that application thereof decreases across-sectional area of at least a portion of the stomach.
 2. Apparatusaccording to claim 1, wherein the set of one or more electrodes includesa first set of one or more electrodes, wherein the apparatus comprises asecond set of one or more electrodes, adapted to be applied to one ormore respective sites in a vicinity of a pyloric sphincter of thestomach, and wherein the control unit is adapted to drive the secondelectrode set to apply an ETC signal configured such that applicationthereof increases a contraction force of the sphincter and extends aperiod of time in which partially-digested food remains in the stomach.3. Apparatus according to claim 1, wherein the control unit is adaptedto configure the ETC signal such that application thereof decreases thecross-sectional area of the portion of the stomach by at least 20%, fora substantially continuous period greater than about one minute. 4.Apparatus according to claim 1, wherein the portion of the stomachincludes a first portion of the stomach, and wherein the control unit isadapted to configure the ETC signal such that ingestion of food by thepatient in conjunction with application of the ETC signal to the firstportion induces stretching of a stretch-receptor in a second portion ofthe stomach that induces a sensation of satiety.
 5. Apparatus accordingto claim 1, wherein the control unit is adapted to drive the electrodeset to apply the signal over a sufficient time period so as to engendera long-term structural change of the stomach.
 6. Apparatus according toclaim 1, wherein the electrode set is adapted to be applied in contactwith muscle tissue of the stomach.
 7. Apparatus according to claim 1,wherein the control unit is adapted to configure the ETC signal suchthat the decreased cross-sectional area impedes passage of ingestathrough the stomach.
 8. Apparatus according to claim 1, wherein thecontrol unit is adapted to configure the ETC signal such thatapplication thereof decreases a volume of the stomach.
 9. Apparatusaccording to claim 1, wherein the control unit is adapted to configure atiming parameter of the ETC signal responsive to timing of naturalgastric electrical activity.
 10. Apparatus according to claim 1, whereinthe control unit is adapted to drive the electrode set to apply the ETCsignal as a series of biphasic pulses.
 11. Apparatus according to claim1, wherein the control unit is adapted to configure the ETC signal tohave a duration of at least about 1 second.
 12. Apparatus according toclaim 11, wherein the control unit is adapted to configure the ETCsignal to have a duration of at least about 3 seconds.
 13. Apparatusaccording to claim 1, and comprising at least one stimulating electrode,wherein the control unit is adapted to drive the stimulating electrodeto apply an excitatory signal to muscle tissue of the stomach inconjunction with driving the electrode set to apply the ETC signal. 14.Apparatus according to claim 13, wherein the control unit is adapted todrive the stimulating electrode to apply gastric pacing pulses to thestomach.
 15. Apparatus according to claim 1, wherein the control unit isadapted to receive a patient signal, input by the patient, and to drivethe electrode set responsive to the patient signal.
 16. Apparatusaccording to claim 15, wherein the control unit is adapted to withholddriving the electrode set responsive to the patient signal. 17.Apparatus according to claim 1, wherein the control unit is adapted todrive the electrode set in accordance with a schedule programmed intothe control unit.
 18. Apparatus according to claim 17, wherein thecontrol unit is adapted to drive the electrode set during at least onemeal eaten by the patient during a 24 hour period, and to withholddriving the electrode set during another meal eaten by the patientduring the 24 hour period.
 19. Apparatus according to claim 17, whereinthe control unit is adapted to withhold driving the electrode set duringtime periods designated as times when the patient generally does noteat.
 20. Apparatus according to claim 1, wherein the control unit isadapted to drive at least one of the electrodes to apply an excitatorypulse in conjunction with the ETC signal.
 21. Apparatus according toclaim 20, wherein the control unit is adapted to drive the at least oneelectrode to apply the excitatory pulse as a biphasic pulse. 22.Apparatus according to claim 20, wherein the control unit is adapted todrive the at least one electrode to initiate applying the ETC signal atleast about 100 ms following a termination of the excitatory pulse. 23.Apparatus according to claim 20, wherein the control unit is adapted todrive the at least one electrode to initiate applying the ETC signalless than about 1000 ms following a termination of the excitatory pulse.24. Apparatus according to claim 1, wherein the control unit is adaptedto drive the electrode set while the patient is eating.
 25. Apparatusaccording to claim 24, wherein the control unit is adapted to receive apatient signal, input by the patient, indicative of the patient eating.26. Apparatus according to claim 25, wherein the control unit is adaptedto receive by way of the patient signal an indication of a nutritionalquality of food being eaten by the patient and to configure a parameterof the ETC signal responsive to the patient signal.
 27. Apparatusaccording to claim 24, and comprising a sensor which is adapted toconvey to the control unit a signal responsive to the patient eating.28. Apparatus according to claim 27, wherein the sensor comprises ablood sugar sensor.
 29. Apparatus according to claim 27, wherein thesensor comprises a mechanical sensor.
 30. Apparatus according to claim27, wherein the sensor comprises a sensing electrode, adapted to becoupled in a vicinity of a gastrointestinal tract of the patient. 31.Apparatus according to claim 30, wherein the sensing electrode comprisesone of the one or more electrodes.
 32. Apparatus according to claim 27,wherein the sensor is adapted to convey the signal responsive to aquantity of food ingested by the patient, and wherein the control unitis adapted to withhold driving the electrode set responsive to thequantity.
 33. Apparatus according to claim 32, wherein the control unitis adapted to withhold driving the electrode set when the quantity isless than a threshold quantity.
 34. Apparatus according to claim 1,wherein the control unit is adapted to configure the ETC signal suchthat application thereof decreases the cross-sectional area of a regionof the stomach, and maintains the decreased cross-sectional area in theregion for a duration greater than about 10 seconds.
 35. Apparatusaccording to claim 1, wherein the control unit is adapted to configurethe ETC signal such that application thereof increases intra-gastricpressure, thereby inducing a sensation of satiety.
 36. Apparatusaccording to claim 1, and comprising a second set of one or moreelectrodes, adapted to be applied to one or more respective sites in avicinity of a lower-esophageal sphincter of the patient, wherein thecontrol unit is adapted to drive the second electrode set to apply asphincter-control signal to the sphincter, configured such thatapplication thereof increases a contraction force generated by thesphincter.
 37. Apparatus for treating a condition, comprising: a set ofone or more electrodes, adapted to be applied to one or more respectivesites in a vicinity of a pyloric sphincter of a stomach of a patient;and a control unit, adapted to drive the electrode set to apply anExcitable-Tissue Control (ETC) signal to the sites, configured such thatapplication thereof increases a contraction force of the sphincter andextends a period of time in which partially-digested food remains in thestomach.
 38. Apparatus according to claim 37, wherein the control unitis adapted to configure the ETC signal such that driving the electrodeset to apply the ETC signal increases the contraction force for asubstantially continuous period greater than about 1 minute. 39.Apparatus according to claim 37, wherein the electrode set is adapted tobe applied in contact with muscle tissue of an antral portion of thestomach.
 40. Apparatus according to claim 37, wherein the electrode setis adapted to be applied in contact with muscle tissue of the sphincter.41. Apparatus according to claim 37, wherein the control unit is adaptedto configure a timing parameter of the ETC signal responsive to timingof natural gastric electrical activity.
 42. Apparatus according to claim37, wherein the control unit is adapted to drive the electrode set toapply the ETC signal as a series of biphasic pulses.
 43. Apparatusaccording to claim 37, and comprising at least one stimulatingelectrode, wherein the control unit is adapted to drive the stimulatingelectrode to apply an excitatory signal to at least one of the sites inconjunction with driving the electrode set to apply the ETC signal. 44.Apparatus according to claim 37, wherein the control unit is adapted todrive the electrode set in accordance with a schedule programmed intothe control unit.
 45. Apparatus according to claim 37, wherein thecontrol unit is adapted to configure the ETC signal to have a durationof at least about 1 second.
 46. Apparatus according to claim 45, whereinthe control unit is adapted to configure the ETC signal to have aduration of at least about 3 seconds.
 47. Apparatus according to claim37, wherein the control unit is adapted to receive a patient signal,input by the patient, and to drive the electrode set responsive to thepatient signal.
 48. Apparatus according to claim 47, wherein the controlunit is adapted to withhold driving the electrode set responsive to thepatient signal.
 49. Apparatus according to claim 37, wherein the controlunit is adapted to drive at least one of the electrodes to apply anexcitatory pulse in conjunction with the ETC signal.
 50. Apparatusaccording to claim 49, wherein the control unit is adapted to drive theat least one electrode to apply the excitatory pulse as a biphasicpulse.
 51. Apparatus according to claim 49, wherein the control unit isadapted to drive the at least one electrode to initiate applying the ETCsignal at least about 100 ms following a termination of the excitatorypulse.
 52. Apparatus according to claim 49, wherein the control unit isadapted to drive the at least one electrode to initiate applying the ETCsignal less than about 1000 ms following a termination of the excitatorypulse.
 53. Apparatus for treating a condition, comprising: a set of oneor more electrodes, adapted to be applied to one or more respectivesites in a vicinity of a body of a stomach of a patient; and a controlunit, adapted to drive the electrode set to apply to the body of thestomach a signal configured such that application thereof increases alevel of contraction of muscle tissue of the body of the stomach, anddecreases a cross-sectional area of a portion of the body of the stomachfor a substantially continuous period greater than about 3 seconds. 54.Apparatus according to claim 53, wherein the control unit is adapted toconfigure the signal such that application thereof decreases thecross-sectional area of the portion for a substantially continuousperiod greater than about 10 seconds.
 55. Apparatus according to claim53, wherein the portion of the stomach includes a first portion of thestomach, and wherein the control unit is adapted to configure the signalsuch that ingestion of food by the patient in conjunction withapplication of the signal induces stretching of a stretch-receptor in asecond portion of the stomach that induces a sensation of satiety. 56.Apparatus according to claim 53, wherein the control unit is adapted todrive the electrode set to apply the signal over a sufficient timeperiod so as to engender a long-term structural change of the stomach.57. Apparatus according to claim 53, wherein the electrode set isadapted to be applied in contact with muscle tissue of the stomach. 58.Apparatus according to claim 53, wherein the control unit is adapted toconfigure the signal such that the decreased cross-sectional areaimpedes passage of ingesta through the stomach.
 59. Apparatus accordingto claim 53, wherein the control unit is adapted to configure the signalsuch that application thereof decreases a volume of the stomach. 60.Apparatus according to claim 53, wherein the control unit is adapted toconfigure the signal such that application thereof decreases thecross-sectional area of a region of the body of the stomach, andmaintains the decreased cross-sectional area in the region for aduration greater than about 10 seconds.
 61. Apparatus according to claim53, wherein the control unit is adapted to configure the signal suchthat application thereof increases intra-gastric pressure, therebyinducing a sensation of satiety.
 62. Apparatus according to claim 53,and comprising a second set of one or more electrodes, adapted to beapplied to one or more respective sites in a vicinity of alower-esophageal sphincter of the patient, wherein the control unit isadapted to drive the second electrode set to apply a sphincter-controlsignal to the sphincter, configured such that application thereofincreases a contraction force generated by the sphincter.
 63. Apparatusaccording to claim 53, wherein the control unit is adapted to receive apatient signal, input by the patient, and to drive the electrode setresponsive to the patient signal.
 64. Apparatus according to claim 63,wherein the control unit is adapted to withhold driving the electrodeset responsive to the patient signal.
 65. Apparatus according to claim53, wherein the control unit is adapted to drive the electrode set inaccordance with a schedule programmed into the control unit. 66.Apparatus according to claim 65, wherein the control unit is adapted todrive the electrode set during at least one meal eaten by the patientduring a 24 hour period, and to withhold driving the electrode setduring another meal eaten by the patient during the 24 hour period. 67.Apparatus according to claim 65, wherein the control unit is adapted towithhold driving the electrode set during time periods designated astimes when the patient generally does not eat.
 68. Apparatus accordingto claim 53, wherein the control unit is adapted to drive the electrodeset while the patient is eating.
 69. Apparatus according to claim 68,wherein the control unit is adapted to receive a patient signal, inputby the patient, indicative of the patient eating.
 70. Apparatusaccording to claim 69, wherein the control unit is adapted to receive byway of the patient signal an indication of a nutritional quality of foodbeing eaten by the patient and to configure a parameter of the signalapplied to the body of the stomach responsive to the patient signal. 71.Apparatus according to claim 68, and comprising a sensor which isadapted to convey to the control unit a signal responsive to the patienteating.
 72. Apparatus according to claim 71, wherein the sensorcomprises a blood sugar sensor.
 73. Apparatus according to claim 71,wherein the sensor comprises a mechanical sensor.
 74. Apparatusaccording to claim 71, wherein the sensor comprises a sensing electrode,adapted to be coupled in a vicinity of a gastrointestinal tract of thepatient.
 75. Apparatus according to claim 74, wherein the sensingelectrode comprises one of the one or more electrodes.
 76. Apparatusaccording to claim 71, wherein the sensor is adapted to convey thesignal responsive to a quantity of food ingested by the patient, andwherein the control unit is adapted to withhold driving the electrodeset responsive to the quantity.
 77. Apparatus according to claim 76,wherein the control unit is adapted to withhold driving the electrodeset when the quantity is less than a threshold quantity.
 78. Apparatusfor treating a condition, comprising: a set of one or more electrodes,adapted to be applied to one or more respective sites in a vicinity of afirst portion of a stomach of a patient; and a control unit, adapted todrive the electrode set to apply to the portion of the stomach a signalconfigured such that application thereof increases a level ofcontraction of muscle tissue of the portion, and configured such thatingestion of food by the patient in conjunction with application of thesignal induces stretching of a stretch-receptor in a second portion ofthe stomach.
 79. Apparatus according to claim 78, wherein the electrodeset is adapted to be applied in contact with muscle tissue of thestomach.
 80. Apparatus according to claim 78, wherein the control unitis adapted to drive the electrode set to apply the signal to a body ofthe stomach, and to configure a parameter-of the signal such that theincreased level of contraction of the muscle tissue impedes passage ofingesta through the stomach and increases a level of tension in a fundicwall of the stomach.
 81. Apparatus according to claim 78, wherein thecontrol unit is adapted to receive a patient signal, input by thepatient, and to drive the electrode set responsive to the patientsignal.
 82. Apparatus according to claim 81, wherein the control unit isadapted to withhold driving the electrode set responsive to the patientsignal.
 83. Apparatus according to claim 78, wherein the control unit isadapted to drive the electrode set in accordance with a scheduleprogrammed into the control unit.
 84. Apparatus according to claim 83,wherein the control unit is adapted to drive the electrode set during atleast one meal eaten by the patient during a 24 hour period, and towithhold driving the electrode set during another meal eaten by thepatient during the 24 hour period.
 85. Apparatus according to claim 83,wherein the control unit is adapted to withhold driving the electrodeset during time periods designated as times when the patient generallydoes not eat.
 86. Apparatus according to claim 78, wherein the controlunit is adapted to drive the electrode set while the patient is eating.87. Apparatus according to claim 86, wherein the control unit is adaptedto receive a patient signal, input by the patient, indicative of thepatient eating.
 88. Apparatus according to claim 87, wherein the controlunit is adapted to receive by way of the patient signal an indication ofa nutritional quality of food being eaten by the patient and toconfigure a parameter of the signal applied to the stomach responsive tothe patient signal.
 89. Apparatus according to claim 86, and comprisinga sensor which is adapted to convey to the control unit a signalresponsive to the patient eating.
 90. Apparatus according to claim 89,wherein the sensor comprises a blood sugar sensor.
 91. Apparatusaccording to claim 89, wherein the sensor comprises a mechanical sensor.92. Apparatus according to claim 89, wherein the sensor comprises asensing electrode, adapted to be coupled in a vicinity of agastrointestinal tract of the patient.
 93. Apparatus according to claim92, wherein the sensing electrode comprises one of the one or moreelectrodes.
 94. Apparatus according to claim 89, wherein the sensor isadapted to convey the signal responsive to a quantity of food ingestedby the patient, and wherein the control unit is adapted to withholddriving the electrode set responsive to the quantity.
 95. Apparatusaccording to claim 94, wherein the control unit is adapted to withholddriving the electrode set when the quantity is less than a thresholdquantity.
 96. Apparatus for treating a condition, comprising: a set ofone or more electrodes, adapted to be applied to one or more respectivesites on an arterial supply of small intestine of a patient; and acontrol unit, adapted to drive the electrode set to apply a signal tothe sites, configured such that application thereof induces constrictionof one or more arteries in the arterial supply and decreases a quantityof digestion products which are absorbed into blood of the patient fromthe small intestine.
 97. Apparatus according to claim 96, wherein thecontrol unit is adapted to configure the signal as an Excitable-TissueControl (ETC) signal.
 98. Apparatus according to claim 96, wherein thecontrol unit is adapted to receive a patient signal, input by thepatient, and to drive the electrode set responsive to the patientsignal.
 99. Apparatus according to claim 98, wherein the control unit isadapted to withhold driving the electrode set responsive to the patientsignal.
 100. Apparatus according to claim 96, wherein the control unitis adapted to drive the electrode set in accordance with a scheduleprogrammed into the control unit.
 101. Apparatus according to claim 100,wherein the control unit is adapted to drive the electrode setsubsequent to initiation of at least one meal eaten by the patientduring a 24 hour period, and to withhold driving the electrode setsubsequent to initiation of another meal eaten by the patient during the24 hour period.
 102. Apparatus according to claim 96, wherein thecontrol unit is adapted to determine an approximate time of initiationof eating, and to initiate driving the electrode set to apply the signalat least ten minutes subsequent thereto.
 103. Apparatus according toclaim 102, wherein the control unit is adapted to determine theapproximate time of initiation of eating responsive to receiving apatient signal, input by the patient.
 104. Apparatus according to claim96, and comprising a sensor which is adapted to convey to the controlunit a signal indicative of food being in a gastrointestinal tract ofthe patient.
 105. Apparatus according to claim 104, wherein the sensorcomprises a blood sugar sensor.
 106. Apparatus according to claim 104,wherein the sensor comprises a mechanical sensor.
 107. Apparatusaccording to claim 104, wherein the sensor comprises a sensingelectrode, adapted to be coupled in a vicinity of the gastrointestinaltract.
 108. Apparatus according to claim 107, wherein the sensingelectrode comprises one of the one or more electrodes.
 109. Apparatusaccording to claim 104, wherein the sensor is adapted to convey thesignal responsive to a quantity of food ingested by the patient, andwherein the control unit is adapted to withhold driving the electrodeset responsive to the quantity.
 110. Apparatus according to claim 109,wherein the control unit is adapted to withhold driving the electrodeset when the quantity is less than a threshold quantity.
 111. Apparatusfor treating a condition, comprising: a set of one or more electrodes,adapted to be applied to one or more respective sites of a stomach of apatient; and a control unit, adapted to drive the electrode set to applyto the stomach, over a sufficient time period, a sequence of pulsesconfigured so as to engender a long-term structural change of thestomach.
 112. Apparatus according to claim 111, wherein the control unitis adapted to configure the sequence of pulses as an Excitatory-TissueControl (ETC) signal.
 113. Apparatus according to claim 111, wherein thecontrol unit is adapted to configure a parameter of the sequence ofpulses such that the application of the pulses over the time period issuch as to engender a continuation of the structural change for at leasttwo days following a termination of the application of the pulses. 114.Apparatus according to claim 111, wherein the control unit is adapted toconfigure a parameter of the sequence of pulses such that theapplication of the pulses over the time period is such as to reduce acharacteristic length of muscle fibers of the stomach.
 115. Apparatusaccording to claim 111, wherein the control unit is adapted to configurea parameter of the sequence of pulses such that the application of thepulses over the time period is such as to reduce a characteristic sizeof the stomach.
 116. Apparatus according to claim 111, wherein thecontrol unit is adapted to drive the electrode set to apply the pulsesfor at least two days.
 117. Apparatus according to claim 116, whereinthe control unit is adapted to drive the electrode set to apply thepulses for at least two weeks.
 118. Apparatus according to claim 111,wherein the control unit is adapted to drive the electrode set inaccordance with a schedule programmed into the control unit. 119.Apparatus according to claim 118, wherein the control unit is adapted todrive the electrode set at times when the patient's stomach is generallyempty.
 120. Apparatus according to claim 118, wherein the control unitis adapted to drive the electrode set during a meal eaten by thepatient.
 121. A method for treating a condition, comprising: applying anExcitable-Tissue Control (ETC) signal to one or more sites in a vicinityof a stomach of a patient; and configuring the ETC signal such thatapplication thereof to the one or more sites decreases a cross-sectionalarea of at least a portion of the stomach.
 122. A method according toclaim 121, and comprising: applying an ETC signal to one or more sitesin a vicinity of a pyloric sphincter of the stomach; and configuring theETC signal applied to the sites in the vicinity of the sphincter suchthat application thereof increases a contraction force of the sphincterand extends a period of time in which partially-digested food remains inthe stomach.
 123. A method according to claim 121, wherein configuringthe signal comprises configuring the signal such that applicationthereof decreases the cross-sectional area of the portion of the stomachfor a substantially continuous period greater than about 1 minute. 124.A method according to claim 121, wherein the portion of the stomachincludes a first portion of the stomach, and wherein configuring thesignal comprises configuring the signal such that, during application ofthe signal, ingestion of food by the patient stretches astretch-receptor in a second portion of the stomach and induces asensation of satiety.
 125. A method according to claim 121, whereinconfiguring the signal comprises configuring the signal such thatapplication thereof over a sufficient time period engenders a long-termstructural change of the stomach.
 126. A method according to claim 121,wherein applying the signal comprises applying the signal to muscletissue of the stomach.
 127. A method according to claim 121, whereinconfiguring the signal comprises configuring the signal such that thedecreased cross-sectional area impedes passage of ingesta through thestomach.
 128. A method according to claim 121, wherein configuring thesignal comprises configuring the signal such that application thereofdecreases a volume of the stomach.
 129. A method according to claim 121,wherein configuring the signal comprises configuring a timing parameterof the signal responsive to timing of natural gastric electricalactivity.
 130. A method according to claim 121, wherein configuring thesignal comprises configuring the signal as a series of biphasic pulses.131. A method according to claim 121, wherein configuring the ETC signalcomprises configuring the signal such that application thereof decreasesthe cross-sectional area of a region of the stomach, and maintains thedecreased cross-sectional area in the region for a duration greater thanabout 10 seconds.
 132. A method according to claim 121, whereinconfiguring the ETC signal comprises configuring the signal such thatapplication thereof increases intra-gastric pressure, thereby inducing asensation of satiety.
 133. A method according to claim 121, andcomprising: applying a sphincter-control signal to one or more sites ina vicinity of a lower-esophageal sphincter of the patient; andconfiguring the sphincter-control signal such that application thereofincreases a contraction force generated by the sphincter.
 134. A methodaccording to claim 121, wherein configuring the signal comprisesconfiguring the signal to have a duration of at least about 1 second.135. A method according to claim 134, wherein configuring the signalcomprises configuring the signal to have a duration of at least about 3seconds.
 136. A method according to claim 121, and comprising applyingan excitatory signal to muscle tissue of the stomach in conjunction withapplying the ETC signal.
 137. A method according to claim 136, whereinapplying the excitatory signal comprises applying gastric pacing pulsesto the stomach.
 138. A method according to claim 121, and comprisingreceiving a patient signal input by the patient, wherein configuring theETC signal comprises configuring the ETC signal responsive to thepatient signal.
 139. A method according to claim 138, whereinconfiguring the ETC signal responsive to the patient signal compriseswithholding application of the ETC signal responsive to the patientsignal.
 140. A method according to claim 121, wherein configuring thesignal comprises configuring the signal in accordance with a schedule.141. A method according to claim 140, wherein applying the signalcomprises: applying the signal during at least one meal eaten by thepatient during a 24 hour period; and withholding applying the signalduring another meal eaten by the patient during the 24 hour period. 142.A method according to claim 140, wherein applying the signal compriseswithholding applying the signal during time periods designated as timeswhen the patient generally does not eat.
 143. A method according toclaim 121, and comprising applying excitatory pulses to one or more ofthe sites in conjunction with applying the ETC signal.
 144. A methodaccording to claim 143, wherein applying the excitatory pulses comprisesapplying the excitatory pulses as biphasic pulses.
 145. A methodaccording to claim 143, wherein applying the ETC signal comprisesinitiating application of the ETC signal at one of the sites at leastabout 100 ms following a termination of an excitatory pulse at the oneof the sites.
 146. A method according to claim 143, wherein applying theETC signal comprises initiating application of the ETC signal at one ofthe sites less than about 1000 ms following a termination of anexcitatory pulse at the one of the sites.
 147. A method according toclaim 121, wherein applying the signal comprises applying the signalwhile the patient is eating.
 148. A method according to claim 147, andcomprising receiving a patient signal, input by the patient, indicativeof the patient eating.
 149. A method according to claim 148, whereinreceiving the patient signal comprises receiving an indication of anutritional quality of food being eaten by the patient.
 150. A methodaccording to claim 149, and comprising receiving a sensor signalresponsive to the patient eating.
 151. A method according to claim 150,wherein receiving the sensor signal comprises receiving an indication ofa blood sugar level of the patient.
 152. A method according to claim150, wherein receiving the sensor signal comprises receiving the sensorsignal responsive to a measurement of a mechanical disposition of agastrointestinal tract of the patient.
 153. A method according to claim150, wherein receiving the sensor signal comprises detecting currentgenerated by muscle tissue of a gastrointestinal tract of the patient.154. A method according to claim 150, wherein receiving the sensorsignal comprises receiving an indication of a quantity of food ingestedby the patient, and wherein applying the ETC signal comprises applyingthe ETC signal if the sensor signal is indicative of the quantity offood being greater than a threshold value.
 155. A method for treating acondition, comprising: applying an Excitable-Tissue Control (ETC) signalto one or more sites in a vicinity of a pyloric sphincter of a stomachof a patient; and configuring the ETC signal such that applicationthereof to the one or more sites increases a contraction force of thesphincter and extends a period of time in which partially-digested foodremains in the stomach.
 156. A method according to claim 155, whereinconfiguring the signal comprises configuring the signal such thatapplication thereof increases the contraction force for a substantiallycontinuous period greater than about 1 minute.
 157. A method accordingto claim 155, wherein applying the signal comprises applying the signalto a site of an antral portion of the stomach.
 158. A method accordingto claim 155, wherein applying the signal comprises applying the signalto muscle tissue of the sphincter.
 159. A method according to claim 155,wherein configuring the signal comprises configuring a timing parameterof the signal responsive to timing of natural gastric electricalactivity.
 160. A method according to claim 155, wherein configuring thesignal comprises configuring the signal as a series of biphasic pulses.161. A method according to claim 155, wherein configuring the signalcomprises configuring the signal in accordance with a schedule.
 162. Amethod according to claim 155, wherein configuring the signal comprisesconfiguring the signal to have a duration of at least about 1 second.163. A method according to claim 162, wherein configuring the signalcomprises configuring the signal to have a duration of at least about 3seconds.
 164. A method according to claim 155, and comprising receivinga patient signal input by the patient, wherein configuring the ETCsignal comprises configuring the ETC signal responsive to the patientsignal.
 165. A method according to claim 164, wherein configuring theETC signal responsive to the patient signal comprises withholdingapplication of the ETC signal responsive to the patient signal.
 166. Amethod according to claim 155, and comprising applying excitatory pulsesto one or more of the sites in conjunction with applying the ETC signal.167. A method according to claim 166, wherein applying the excitatorypulses comprises applying the excitatory pulses as biphasic pulses. 168.A method according to claim 166, wherein applying the ETC signalcomprises initiating application of the ETC signal at one of the sitesat least about 100 ms following a termination of an excitatory pulse atthe one of the sites.
 169. A method according to claim 166, whereinapplying the ETC signal comprises initiating application of the ETCsignal at one of the sites less than about 1000 ms following atermination of an excitatory pulse at the one of the sites.
 170. Amethod for treating a condition, comprising: applying a signal to one ormore sites in a vicinity of a body of a stomach of a patient; andconfiguring the signal such that application thereof to the one or moresites increases a level of contraction of muscle tissue of a portion ofthe body of the stomach, and decreases a cross-sectional area of theportion for a substantially continuous period greater than about 3seconds.
 171. A method according to claim 170, wherein configuring thesignal comprises configuring the signal so as to decrease thecross-sectional area of the portion for a substantially continuousperiod greater than about 10 seconds.
 172. A method according to claim170, wherein the portion of the stomach includes a first portion of thestomach, and wherein configuring the signal comprises configuring thesignal such that, during application of the signal, ingestion of food bythe patient stretches a stretch-receptor in a second portion of thestomach and induces a sensation of satiety.
 173. A method according toclaim 170, wherein configuring the signal comprises configuring thesignal such that application thereof over a sufficient time periodengenders a long-term structural change of the stomach.
 174. A methodaccording to claim 170, wherein applying the signal comprises applyingthe signal to muscle tissue of the body of the stomach.
 175. A methodaccording to claim 170, wherein configuring the signal comprisesconfiguring the signal such that the decreased cross-sectional areaimpedes passage of ingesta through the body of the stomach.
 176. Amethod according to claim 170, wherein configuring the signal comprisesconfiguring the signal such that application thereof decreases a volumeof the body of the stomach.
 177. A method according to claim 170,wherein configuring the signal comprises configuring the signal suchthat application thereof decreases the cross-sectional area of a regionof the stomach, and maintains the decreased cross-sectional area in theregion for a duration greater than about 10 seconds.
 178. A methodaccording to claim 170, wherein configuring the signal comprisesconfiguring the signal such that application thereof increasesintra-gastric pressure, thereby inducing a sensation of satiety.
 179. Amethod according to claim 170, and comprising: applying asphincter-control signal to one or more sites in a vicinity of alower-esophageal sphincter of the patient; and configuring thesphincter-control signal such that application thereof increases acontraction force generated by the sphincter.
 180. A method according toclaim 170, and comprising receiving a patient signal input by thepatient, wherein configuring the signal comprises configuring the signalresponsive to the patient signal.
 181. A method according to claim 180,wherein configuring the signal responsive to the patient signalcomprises withholding application of the signal responsive to thepatient signal.
 182. A method according to claim 170, whereinconfiguring the signal comprises configuring the signal in accordancewith a schedule.
 183. A method according to claim 182, wherein applyingthe signal comprises: applying the signal during at least one meal eatenby the patient during a 24 hour period; and withholding applying thesignal during another meal eaten by the patient during the 24 hourperiod.
 184. A method according to claim 182, wherein applying thesignal comprises withholding applying the signal during time periodsdesignated as times when the patient generally does not eat.
 185. Amethod according to claim 170, wherein applying the signal comprisesapplying the signal while the patient is eating.
 186. A method accordingto claim 185, and comprising receiving a patient signal, input by thepatient, indicative of the patient eating.
 187. A method according toclaim 186, wherein receiving the patient signal comprises receiving anindication of a nutritional quality of food being eaten by the patient.188. A method according to claim 185, and comprising receiving a sensorsignal responsive to the patient eating.
 189. A method according toclaim 188, wherein receiving the sensor signal comprises receiving anindication of a blood sugar level of the patient.
 190. A methodaccording to claim 188, wherein receiving the sensor signal comprisesreceiving the sensor signal responsive to a measurement of a mechanicaldisposition of a gastrointestinal tract of the patient.
 191. A methodaccording to claim 188, wherein receiving the sensor signal comprisesdetecting current generated by muscle tissue of a gastrointestinal tractof the patient.
 192. A method according to claim 188, wherein receivingthe sensor signal comprises receiving an indication of a quantity offood ingested by the patient, and wherein applying the signal comprisesapplying the signal if the sensor signal is indicative of the quantityof food being greater than a threshold value.
 193. A method for treatinga condition, comprising: applying a signal to one or more sites in avicinity of a first portion of a stomach of a patient; and configuringthe signal such that the application thereof increases a level ofcontraction of muscle tissue of the portion and stretches astretch-receptor in a second portion of the stomach.
 194. A methodaccording to claim 193, wherein applying the signal comprises applyingthe signal to muscle tissue of the stomach.
 195. A method according toclaim 193, wherein applying the signal comprises applying the signal toa body of the stomach, and wherein configuring the signal comprisesconfiguring a parameter of the signal such that the increased level ofcontraction of the muscle tissue impedes passage of ingesta through thestomach and increases a level of tension in a fundic wall of thestomach.
 196. A method according to claim 193, and comprising receivinga patient signal input by the patient, wherein configuring the signalcomprises configuring the signal responsive to the patient signal. 197.A method according to claim 196, wherein configuring the signalresponsive to the patient signal comprises withholding application ofthe signal responsive to the patient signal.
 198. A method according toclaim 193, wherein configuring the signal comprises configuring thesignal in accordance with a schedule.
 199. A method according to claim198, wherein applying the signal comprises: applying the signal duringat least one meal eaten by the patient during a 24 hour period; andwithholding applying the signal during another meal eaten by the patientduring the 24 hour period.
 200. A method according to claim 198, whereinapplying the signal comprises withholding applying the signal duringtime periods designated as times when the patient generally does noteat.
 201. A method according to claim 193, wherein applying the signalcomprises applying the signal while the patient is eating.
 202. A methodaccording to claim 201, and comprising receiving a patient signal, inputby the patient, indicative of the patient eating.
 203. A methodaccording to claim 202, wherein receiving the patient signal comprisesreceiving an indication of a nutritional quality of food being eaten bythe patient.
 204. A method according to claim 201, and comprisingreceiving a sensor signal responsive to the patient eating.
 205. Amethod according to claim 204, wherein receiving the sensor signalcomprises receiving an indication of a blood sugar level of the patient.206. A method according to claim 204, wherein receiving the sensorsignal comprises receiving the sensor signal responsive to a measurementof a mechanical disposition of a gastrointestinal tract of the patient.207. A method according to claim 204, wherein receiving the sensorsignal comprises detecting current generated by muscle tissue of agastrointestinal tract of the patient.
 208. A method according to claim204, wherein receiving the sensor signal comprises receiving anindication of a quantity of food ingested by the patient, and whereinapplying the signal comprises applying the signal if the sensor signalis indicative of the quantity of food being greater than a thresholdvalue.
 209. A method for treating a condition, comprising: applying asignal to one or more sites on an arterial supply of small intestine ofa patient; and configuring the signal such that application thereof tothe sites induces constriction of one or more arteries in the arterialsupply and decreases a quantity of digestion products which are absorbedinto blood of the patient from the small intestine.
 210. A methodaccording to claim 209, applying the signal comprises applying anExcitable-Tissue Control (ETC) signal.
 211. A method according to claim209, and comprising receiving a patient signal input by the patient,wherein configuring the signal comprises configuring the signalresponsive to the patient signal.
 212. A method according to claim 211,wherein configuring the signal responsive to the patient signalcomprises withholding application of the signal responsive to thepatient signal.
 213. A method according to claim 209, whereinconfiguring the signal comprises configuring the signal in accordancewith a schedule.
 214. A method according to claim 213, wherein applyingthe signal comprises: applying the signal subsequent to initiation of atleast one meal eaten by the patient during a 24 hour period; andwithholding applying the signal subsequent to initiation of another mealeaten by the patient during the 24 hour period.
 215. A method accordingto claim 209, and comprising determining an approximate time ofinitiation of eating, wherein applying the signal comprises initiatingapplication of the signal at least ten minutes subsequent to theapproximate time of initiation of eating.
 216. A method according toclaim 215, and comprising receiving a patient signal, input by thepatient, indicative of the approximate time of initiation of eating.217. A method according to claim 209, and comprising receiving a sensorsignal indicative of food being in a gastrointestinal tract of thepatient.
 218. A method according to claim 217, wherein receiving thesensor signal comprises receiving an indication of a blood sugar levelof the patient.
 219. A method according to claim 217, wherein receivingthe sensor signal comprises receiving the sensor signal responsive to ameasurement of a mechanical disposition of the gastrointestinal tract.220. A method according to claim 217, wherein receiving the sensorsignal comprises detecting current generated by muscle tissue of thegastrointestinal tract.
 221. A method according to claim 217, whereinreceiving the sensor signal comprises receiving an indication of aquantity of food ingested by the patient, and wherein applying thesignal comprises applying the signal if the sensor signal is indicativeof the quantity of food being greater than a threshold value.
 222. Amethod for treating a condition, comprising: applying a sequence ofpulses over a time period to one or more sites of a stomach of apatient; and configuring the sequence of pulses such that applicationthereof to the one or more sites engenders a long-term structural changeof the stomach.
 223. A method according to claim 222, wherein applyingthe sequence of pulses comprises applying an Excitatory-Tissue Control(ETC) signal.
 224. A method according to claim 222, wherein configuringthe sequence of pulses comprises configuring a parameter of the sequenceof pulses such that the application of the pulses over the time periodis such as to engender a continuation of the structural change for atleast two days following a termination of the application of the pulses.225. A method according to claim 222, wherein configuring the sequenceof pulses comprises configuring a parameter of the sequence of pulsessuch that the application of the pulses over the time period is such asto reduce a characteristic length of muscle fibers of the stomach. 226.A method according to claim 222, wherein configuring the sequence ofpulses comprises configuring a parameter of the sequence of pulses suchthat the application of the pulses over the time period is such as toreduce a characteristic size of the stomach.
 227. A method according toclaim 222, wherein applying the sequence of pulses over the time periodcomprises applying the sequence of pulses for at least two days.
 228. Amethod according to claim 227, wherein applying the sequence of pulsesover the time period comprises applying the sequence of pulses for atleast two weeks.
 229. A method according to claim 222, whereinconfiguring the sequence of pulses comprises configuring the sequence ofpulses in accordance with a schedule.
 230. A method according to claim229, wherein applying the sequence of pulses comprises applying thesequence of pulses at times when the patient's stomach is generallyempty.
 231. A method according to claim 229, wherein applying thesequence of pulses comprises applying the sequence of pulses during ameal eaten by the patient.